Case report: Immunohistochemical characterization of pulmonary corpora amylacea in an autopsy case, with special reference to its pathogenesis

Pulmonary corpora amylacea (PCA) is rare. We report here an autopsy case of a Japanese woman in her eighties who harbored numerous PCAs in both lungs. Multiple infarctions were found in the brainstem as the cause of her death. In an attempt to characterize these PCAs, several antibodies were used, including those to surfactant protein (SP)-A, SP-D, KL-6, epithelial membrane antigen (EMA), pancytokeratins, and macrophages. PCAs were almost all positive for SP-A, in concentric lamellar fashion, some with niduses. Internal positivity of PCAs was observed on diastase-digested PAS reaction. Staining for SP-D was negative. More than half of the PCAs were covered by macrophages, indicating that they were foreign bodies. With regard to the pathogenesis of PCAs, we believe that SP-A is one of the important factors whether niduses are present or absent, and that SP-A is gradually deposited on the surfaces of PCAs in lamellar fashion. Our findings indicate that SP-A is required for the formation of PCAs, and suggest that pulmonary dysfunction, leading to an imbalance between the production of SP-A and its absorption, might be the cause of the deposition of PAS-positive glycoproteins and/or SP-A as PCAs.